Ireland is to double as Scotland in yet another historical film epic - this time about Mary Queen of Scots, with Scarlett Johansson in the title role.

A decade after Ireland served as the backdrop to Mel Gibson's Braveheart, about Scottish rebel William Wallace, Irish army reservists are once again preparing to step into the breach as battlefield extras.

Agreement has been reached in principle for six to seven weeks of the film to be shot on Irish locations, followed by three weeks in Scotland. Crucially, Ireland is also set to provide the backdrop for a series of battle scenes - paving the way for lucrative tourism spin-offs.

The development comes as many involved with the British film industry admit that 2008 is likely to be a tough year, not least due to the dollar-pound exchange rate.

Based on a script originally developed by BBC Films with Jimmy McGovern, the writer of Cracker, the film is being produced by two Americans. The principal financier is Capitol Films, a UK-based company. The Irish production company Element Pictures is bringing generous Irish tax incentives to the table, along with investment by the Irish Film Board.

A number of locations have been looked at, including Cahir Castle in Co Tipperary, built in the 12th century and one of the largest in Ireland.

As the holder of a Danish passport, Johansson will benefit from tax incentives that also apply to salaries paid to any EU citizen during filming in Ireland. Post-production will take place in London.